Fig. 1.

Regulation of body water balance in response to body water deficit typical of exercise/fluid restriction for a 70 kg individual. Schematic includes the estimated magnitude of dehydration (2% body mass loss) required to stimulate the osmotic-dependent response for compensatory water conservation and acquisition (thirst). A change in total body water is equated with a change in body mass (1 L = 1 kg), whereby dehydration is then expressed as a percentage of body mass in accordance with: (Δ body mass/initial body mass) × 100 or, for this example, (1.4 kg/70 kg) × 100 = 2%. AVP arginine vasopressin, Posm plasma osmolality, TBW total body water